1. Viewing Package Dependencies

1.1 Forward Dependencies

Which packages it depends on

• List dependencies

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apt-cache depends apparmor

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apparmor
  Depends: debconf             # 必须
  Depends: lsb-base            # 必须
 |Depends: debconf             # 必须
  Depends: <debconf-2.0>       # 多选一
    cdebconf
    debconf
  Depends: libc6               # 必须
  Breaks: apparmor-profiles-extra # 不兼容
  Breaks: fcitx-data           # 不兼容
  Breaks: snapd                # 不兼容
  Suggests: apparmor-profiles-extra # 建议安装
  Suggests: apparmor-utils     # 建议安装
  Replaces: fcitx-data         # 用于替代后者

• View installed dependencies

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apt-cache depends --installed apparmor

• View detailed dependencies

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apt show apparmor
dpkg -s apparmor | grep -E '^(Package|Version|Depends|Pre-Depends|Recommends|Suggests|Conflicts|Breaks|Replaces):'

1.2 Reverse Dependencies

Who depends on this package

• List all packages that may depend on this package

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apt-cache rdepends golang-github-containers-common

• Show only installed reverse dependencies

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apt-cache rdepends --installed golang-github-containers-common

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golang-github-containers-common
Reverse Depends:
  skopeo
  podman
  buildah
  podman

• Explain why a package is installed

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aptitude why golang-github-containers-common

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i   devscripts  Suggests autopkgtest
p   autopkgtest Suggests podman
p   podman      Depends  golang-github-containers-common

• Explain why something is not installed or cannot be installed

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aptitude why-not golang-github-containers-common

1.3 Dependency Trees and Conflicts

Simulated installs and reverse file lookups

• View the dependency resolution tree

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apt-cache showpkg apparmor

• Simulate installing a single package

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apt install --simulate apparmor

• Simulate a whole upgrade

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apt-get -s upgrade

• Look up which package a file belongs to

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dpkg -S /usr/bin/apparmor

• List which files a package installed

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dpkg -L apparmor

1.4 Third-Party and Non-Official Repository Packages

Snap, manual installs, and similar cases need separate investigation

• View which repository a package comes from

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apt-cache policy apparmor

• View the configured apt sources

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cat /etc/apt/sources.list /etc/apt/sources.list.d/*.list

• View Snap packages

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snap list

• View the binary path and type

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which apparmor && file "$(which apparmor)"

2. Viewing a Package’s Change History

2.1 Local Change Records

When it was last installed, upgraded, or removed

• View the APT operation history

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less /var/log/apt/history.log

• View dpkg state changes

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less /var/log/dpkg.log

• Filter history by package name

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zgrep -h apparmor /var/log/apt/history.log* /var/log/dpkg.log*
grep -E 'install|upgrade|remove' /var/log/apt/history.log | grep apparmor

• Example history.log record format

Start-Date: 2026-07-10  14:32:01
Commandline: apt upgrade
Upgrade: apparmor:amd64 (3.0.4-2ubuntu2, 1.18.0-6ubuntu14.5)
End-Date: 2026-07-10  14:32:15

2.2 Upstream Change Records

What has changed for this package in the repository

• View the changelog

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apt changelog apparmor | less

• View available versions and source priorities

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apt-cache policy apparmor

• List all available versions in the repository

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apt-cache madison apparmor

Ubuntu also officially lets you look up the changelog and bugs for the corresponding source package on Launchpad, which is good for seeing fix records that span multiple versions.

2.3 Comparing Version Differences

File changes before and after an upgrade

• View the contents of a cached deb

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dpkg-deb -c /var/cache/apt/archives/apparmor_*.deb | head

• Export the currently installed file list

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dpkg -L apparmor > /tmp/apparmor-files.txt

3. Pinning a Package Version

3.1 Locking a Version with hold

Prevent a specified package from being upgraded

• Lock a package

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apt-mark hold apparmor

• View locked packages

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apt-mark showhold

• Unlock

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apt-mark unhold apparmor

Suitable for core middleware (apparmor, mysql, the kernel) and versions with known breaking changes.

3.2 Specifying a Version at Install Time

Install or downgrade to a specified version

• Find the version

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apt-cache madison apparmor

• Simulate the install

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apt install --simulate apparmor=3.0.4-2ubuntu2

• Install the specified version

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apt install apparmor=3.0.4-2ubuntu2

3.3 Previewing Before an Upgrade

See which packages will be touched before you run it

• List upgradable packages

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apt list --upgradable

• Simulate upgrade

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apt-get -s upgrade

• Simulate dist-upgrade

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apt-get -s dist-upgrade

• Install apt-listchanges to show change descriptions

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apt install apt-listchanges